Duplicative transmission of page records in a page message

ABSTRACT

Disclosed herein are methods and systems that may take advantage of unused space in general page messages (GPMs) by including multiple instances of a given page in the same GPM, in an effort to improve the chances that the intended mobile station receives the page. An exemplary paging method involves: (a) before a transmission of a general page message (GPM) that is formatted to include up to a maximum number of page records, making a determination that less than the maximum number of page records are scheduled to be included in the GPM; (b) in response to the determination, selecting, from the page records that are scheduled to be included in the GPM, at least one page record for which to include two or more instances in the GPM; and (c) transmitting the GPM, wherein two or more instances of the at least one selected page record are included in the transmission of the GPM.

BACKGROUND

In a typical cellular wireless communication system, an area is dividedgeographically into a number of cell sites, each defined by a radiofrequency (RF) radiation pattern from a respective base station. Thebase stations of the cells are then coupled to a switch or gateway(which collectively may be referred to as a “switching system”) thatprovides connectivity with a transport network and/or to a signalingnetwork. When a mobile station (i.e., wireless communication device),such as a cellular telephone, personal digital assistant, pager, orappropriately equipped portable computer, for instance, is positioned ina cell, the mobile station may then communicate via an RF air interfacewith the base station of the cell. Consequently, a communication pathcan be established between the mobile station and the network, via theair interface, the base station and the switch. In this way, the basestation(s) and switches work in combination to function as a radioaccess network (RAN), providing mobile stations with RF access to engagein wireless communications, such as telephone calls or Internetcommunications.

In general, the air interface used for communications from a basestation to mobile stations (i.e., the forward link) may be divided intoa number of channels, including traffic channels used to carry bearertraffic (e.g., voice or other user data) and control channels used tocarry overhead messages. Depending on the wireless technology used, theair interface can be divided into these channels through code divisionmultiplexing (with each channel defined by modulation with a specificcode), time division multiplexing (with each channel defined as asegment of time), frequency division multiplexing (with each channeldefined by modulation with a specific frequency), and/or some othermechanism.

When a RAN receives a request to connect a call to a mobile station(which may be for various different types of communications, such asvoice communications or data communications), the RAN will typicallypage the mobile station in an effort to determine whether the mobilestation is available to receive the call. In practice, for instance, theswitching system may direct a base station to broadcast a page to themobile station over an air-interface paging channel. If the mobilestation receives the page, the mobile station typically responds with anacknowledgment message back to the RAN, which would cause the switchingsystem to continue setup of the call to the mobile station.

If a base station has numerous pages to send, then the paging channelcan become congested, which may delay call setup or even result in apage not reaching the intended mobile station. As such, base stationscommonly group a certain number of pages (that are typically intendedfor different mobile stations) into a general page message (GPM) fortransmission via the paging channel. In this arrangement, each pageincluded in the GPM may take the form of a page record, which isgenerated by the base station upon receipt of an indication from aswitch that an incoming communication has been received for a mobilestation. Furthermore, to conserve bandwidth, and so that more pages canbe transmitted in a GPM of the same size, each page record in a pagemessage may be concatenated.

OVERVIEW

A radio access network (RAN) is typically configured to format generalpage messages (GPMs) such that a certain number of page records may beincluded in each GPM. For example, in a typical CDMA system operatingunder the IS-2000 protocol, each GPM may be formatted such that up tofour page records may be included in a single GPM. Alternatively, pagerecords may be concatenated so that up to eight page records may beincluded in a single GPM of the same size.

In practice, the number of pages that can be included in a given GPM maybe greater than the number of pages that a base station actually needsto send in the GPM. In this scenario, there may be unused space in theGPM. Accordingly, methods and systems are disclosed herein to detectwhen there is unused space in a GPM, and to take advantage of the unusedspace to increase the probability that at least one of the page recordsin the GPM successfully reaches the intended mobile station. Inparticular, when unused space exists in a given GPM, a base station mayuse this space to include multiple instances of at least one page recordthat is already scheduled for transmission in the GPM.

Including multiple instances of a given page record may help to increasethe probability that the intended mobile station receives at least oneinstance of the page record successfully. For example, in the eventthere is a bit error that affects one instance of a page record in agiven GPM, a second instance may still be received by the intendedmobile station. It should be understood, however, that exemplaryembodiments, in which multiple instances of a page record may beincluded in a given GPM, may be useful in other scenarios, and may alsoprovide other benefits, without departing from the scope of theinvention.

In one aspect, an exemplary paging method involves: (a) before atransmission of a general page message (GPM) that is formatted toinclude up to a maximum number of page records, making a determinationthat less than the maximum number of page records are scheduled to beincluded in the GPM; (b) in response to the determination, selecting,from the page records that are scheduled to be included in the GPM, atleast one page record for which to include two or more instances in theGPM; and (c) transmitting the GPM, wherein two or more instances of theat least one selected page record are included in the transmission ofthe GPM.

In an exemplary method, the selection of the at least one page recordfor which to include two or more instances may be based on one or morefactors, which may include, but are not limited to: (i) a randomselection process, (ii) the attempt counts for the one or more of thepage records that are scheduled to be included in the GPM, (iii) thepage-types of the scheduled page records, (iv) the service-tiersassociated with the mobile stations to which the scheduled page recordsare directed, (v) the RF conditions being experienced by the mobilestations to which the scheduled page records are directed, and (vi)whether or not each of the mobile stations to which the scheduled pagerecords are directed is hybrid mobile station.

In another aspect, an exemplary system may include: (i) a tangiblecomputer-readable medium; and (ii) program instructions stored on thetangible computer-readable medium and executable by at least oneprocessor to: (a) before a transmission of a general page message (GPM)that is formatted to include up to a maximum number of page records,make a determination that less than the maximum number of page recordsare scheduled to be included in the GPM; (b) in response to thedetermination, select at least one page record from the page recordsthat are scheduled to be included in the GPM, for which to include twoor more instances in the GPM; and (c) initiate the transmission of theGPM, wherein two or more instances of the at least one selected pagerecord are included in the transmission of the GPM.

These as well as other aspects, advantages, and alternatives, willbecome apparent to those of ordinary skill in the art by reading thefollowing detailed description, with reference where appropriate to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the present invention is described hereinwith reference to the drawings, in which:

FIG. 1 is a block diagram of a wireless communication system in which anexemplary embodiment may be employed;

FIG. 2 is a block diagram illustrating a portion of the coverage area inan exemplary radio access network;

FIG. 3 is flow chart illustrating a method according to an exemplaryembodiment;

FIG. 4 is flow chart illustrating another method according to anexemplary embodiment;

FIGS. 5A and 5B are block diagrams illustrating an exemplary generalpage message before and after a base station carries out an exemplarymethod; and

FIGS. 6A, 6B, and 6C are block diagrams illustrating another exemplarygeneral page message before and after a base station carries out anexemplary method.

DETAILED DESCRIPTION

Exemplary embodiments of the present invention are described herein. Itshould be understood that the word “exemplary” is used herein to mean“serving as an example, instance, or illustration.” Any embodimentdescribed herein as “exemplary” is not necessarily to be construed aspreferred or advantageous over other embodiments. Further, those skilledin the art will understand that changes and modifications may be made tothese embodiments without departing from the true scope and spirit ofthe invention, which is defined by the claims.

The present invention will be described by way of example with referenceto Code Division Multiple Access (“CDMA”) communications in general, andin particular, to communications under EIA/TIA/IS-2000 Rel. 0, A(referred to herein as “IS-2000”). As described below, IS-2000 appliesto both circuit-cellular and packet-data communications. Under IS-2000,packet-data communications are referred to as “1X-RTT” communications,also abbreviated as just “1X.” However, since IS-2000 supports bothcircuit voice and packet data communications, the term 1X (or 1X-RTT) issometimes used to more generally refer to the IS-2000 air interface,without regard to the particular type of communication carried. Itshould be understood that the present invention may apply to otherwireless voice and data protocols including, without limitation,EIA/TIA/IS-856 Rel. 0, A, or other version thereof (referred to as“IS-856” or “EVDO”), IS-95, and GSM, among others.

Exemplary embodiments generally involve including multiple instances ofone or more selected page records, when space is available in a GPM todo so. Accordingly, references may be made to including a page record“in duplicate.” Referring to a page record as being included “induplicate” should not be construed to limit the number of instancesincluded in the GPM to two instances. Rather, it should be understoodthat when a page record is referred to as being including in duplicate,multiple instances (i.e., two or more instances) of the page record maybe included in the GPM.

I. Exemplary Network Architecture

FIG. 1 shows a simplified block diagram of a wireless communicationsystem 100 in which an exemplary embodiment may be employed. Thecommunication system 100 is configured to provide wireless service to amobile station 102, and includes a base transceiver station (BTS) 104, abase station controller (BSC) 106, and a mobile switching center (MSC)108. BTS 104, BSC 106, MSC 108 may be referred to as part of a largerradio access network (RAN) implemented by a service provider. As shown,mobile station 102 communicates over an air interface 103 with a BTS104, which is then coupled or integrated with a BSC 106. Transmissionsover air interface 103 from BTS 104 to mobile station 102 represent theforward link to the mobile station, while transmissions over interface103 from mobile station 102 to BTS 104 represent the reverse link.

BSC 106 is in turn connected to MSC 108, which acts to controlassignment of air traffic channels (e.g., over air interface 103), andprovides access to wireless circuit-switched services such ascircuit-voice and circuit-data (e.g., modem-based packet data) service.As represented by its connection to a public switched telephone network(PSTN) 112, MSC 108 is also coupled with one or more other MSCs or othertelephony circuit switches in the operator's (or in a differentoperator's) network, thereby supporting user mobility across MSCregions, and local and long-distance landline telephone services. Alsoconnected to MSC 108 is home location register (HLR) 110, which supportsmobility-related aspects of subscriber services, such as dynamictracking of subscriber registration location and/or verification ofservice privileges.

As shown, BSC 106 is also connected to a packet data serving node (PDSN)116 by way of packet control function (PCF) 114. PDSN 116 in turnprovides connectivity with a packet-switched network 118, such as theInternet and/or a wireless carrier's private core packet-network.Sitting as nodes on network 118 are, by way of example, anauthentication, authorization, and accounting (AAA) server 120, amobile-IP home agent (HA) 122, and a remote computer 124.

With the arrangement described above, a mobile station 102 can engage inwireless voice and/or wireless packet-data (e.g., 1X-RTT or EVDO)communications. Taking an originating call from mobile station 102 as anexample, mobile station 102 first sends an origination request over airinterface 103 and via the BTS 104 and BSC 106 to MSC 108. The MSC thensignals back to the BSC directing the BSC to assign an air interfacetraffic channel for use by the mobile station. For a voice call, the MSCuses well-known circuit protocols to signal call setup and establish acircuit connection to a destination switch that can then connect thecall to a called device (e.g., landline phone or another mobilestation). For a packet-data session, the BSC signals to the PDSN 216 byway of PCF 214. The PDSN 216 and mobile station 102 then negotiate toestablish a data link layer connection, such as a point to pointprotocol (PPP) session. Further, the PDSN 216 sends a foreign agentadvertisement that includes a challenge value to the mobile station, andthe mobile station 102 responds with a mobile-IP registration request(MIP RRQ), including a response to the challenge, which the PDSNforwards to HA 222. The HA then assigns an IP address for the mobilestation 102 to use, and the PDSN passes that IP address via the BSC tothe mobile station.

Generally, it should be understood that the depiction of just one ofeach network element in FIG. 1 is illustrative, and there could be morethan one of any of them, as well as other types of elements not shown.The particular arrangement shown in FIG. 1 should not be viewed aslimiting with respect to the present invention. Further, the networkcomponents that make up a wireless communication system such as system100 are typically implemented as a combination of one or more integratedand/or distributed platforms, each comprising one or more computerprocessors, one or more forms of computer-readable storage (e.g., disksdrives, random access memory, etc.), one or more communicationinterfaces for interconnection between elements and the network andoperable to transmit and receive the communications and messagesdescribed herein, and one or more computer software programs and relateddata (e.g., machine-language instructions and program and user data)stored in the one or more forms of computer-readable storage andexecutable by the one or more computer processors to carry out thefunctions, steps, and procedures of the various embodiments of thepresent invention described herein. Similarly, a communication devicesuch as exemplary mobile station 102 typically comprises auser-interface, I/O components, a communication interface, a tonedetector, a processing unit, and data storage, all of which may becoupled together by a system bus or other mechanism.

Throughout this description, the term “base station” may be used torefer to a BTS, a BSC, or a combination of one or more BTSs and a BSC,for instance. Further, it should be understood that actions that aregenerally described as being carried out by the RAN (or simply by the“network”) may be carried out by various different entities orcombinations of entities in the RAN. Moreover, actions described asbeing carried out by one network entity may also be carried out by othernetwork entities, without departing from the scope of the invention.

II. Exemplary Paging Functionality

In each coverage area, the serving BTS 104 preferably broadcasts aspecification of paging channels defined in the coverage area, so that amobile station 102 beginning to operate in the coverage area candetermine how many paging channels the coverage area includes and, ifmore than one, can determine which paging channel to monitor. By way ofexample, this specification may be an indication in an overhead messagereferred to as a system parameters message, which the base stationbroadcasts periodically. Further, the specification may define thepaging channels expressly by particular coding parameters or, as notedabove may simply indicate how many paging channels there are, which mayinherently define the paging channels if a sequence of possible pagingchannels exists.

A mobile station 102 that has no active data session or voice call(i.e., no assigned traffic channel), but is otherwise operational, issaid to be in an “idle” state or mode. While in the idle state, themobile station 102 periodically scans the air interface forcommunication from the wireless communication system. More specifically,the mobile station 102 monitors the paging channel for page messagesfrom its serving base station 104 and/or other base stations. Pagemessages are used to send the mobile station information, alerts, andrequests during times when the mobile station isn't engaged in acommunication (i.e., when the mobile station is idle). For instance, themobile station may be alerted of an incoming call or other incomingcommunications via a page message.

Paging is typically initiated when an MSC 108 receives an indication ofan incoming communication for a mobile station, or when the MSCotherwise determines that a mobile station needs to be paged. Theindication normally includes an identifier of the mobile station, suchas a Network Access Identifier (NAI), a Mobile Directory Number (MDN), aMobile Identification Number (MIN), an International Mobile SubscriberIdentifier (IMSI), an electronic serial number (ESN), and a mobileequipment identifier (MEID). The MSC 108 may then transmit someindication that the mobile station should be paged to the appropriateBTS 104 (or possibly to multiple BTSs). In turn, the BTS 104 may use themobile-station identifier to generate a page record, which the BTS maythen transmit in a coverage area or coverage areas where it believes themobile station is most likely to receive the page. When a mobile station102 successfully receives a page, the mobile station may reply to theRAN with a page-response message (PRM). After receiving the PRM, the RANmay then assign the one or more traffic channels to the mobile station.

One metric of the paging effectiveness in a wireless coverage area isthe wireless coverage area's paging success rate (PSR). The more oftenpaging procedures in the wireless coverage area result in the successfulpaging of a WCD, the higher the PSR. PSR may be measured for a coveragearea as a whole (i.e., the percentage of all GPMs in a given coveragearea to which a WCD responds with a PRM). However, PSR may also bemeasured on a per-WCD basis (e.g., the percentage of pages to aparticular WCD to which the WCD responds with a PRM), on a per-WCD andper-coverage area basis (e.g., the percentage of pages to a particularWCD in a particular coverage area to which the WCD responds with a PRM),or on another basis altogether.

A. General Page Messages

In a further aspect, a RAN, and in particular a BTS 104 in the RAN, maybe configured to concurrently page a number of mobile stations in agiven sector. To do so, a BTS may be configured to transmit a GeneralPage Message (GPM) that includes multiple page records, with each pagerecord being intended for a different mobile station. (Each “pagerecord” included in a GPM may also be referred to simply as a “page”.)

Each page record may contain error detection bits, such as a checksum.Thus, once the mobile station receives such a GPM, it will look for apage record directed to it (e.g., a page record with the mobilestation's MIN or IMSI, for instance). If the mobile station determinesthat it is being paged, the mobile station typically will validate thechecksum in the page record. Then, if the checksum indicates that thereare no bit errors in the page record, the mobile station may reply tothe RAN with a page-response message (PRM). However, if the checksumindicates that one or more bits in the page record are in error, themobile station may discard the GPM, or possibly indicate to the RAN thatthere was an error.

Normally, a GPM occupies two half-frames of a paging channel slot, andtherefore each paging channel slot would support at most four pagerecords. However, multiple page records within a GPM may be concatenatedso that more mobile stations may be paged per GPM. For example, two pagerecords can be concatenated so that they can be transmitted in a singleGPM that occupies between two and three half-frames. Further,concatenation schemes may be defined so that even more page records,such as four or eight page records for instance, may be concatenated ina single 80 ms paging-channel slot. Other concatenation schemesinvolving varying degrees of concatenation are also possible.

B. Page Scheduling

In an exemplary embodiment, each base station (e.g., BTS 104 and/or BSC106) may include a scheduler 126, which functions to schedule pagerecords received from switches, such as MSC 108, as they are received.As such, the scheduler 126 may function to group page records into GPMs,and schedule the transmission of the GPMs during appropriatepaging-channel slots. While the scheduler 126 is shown as beingconnected to BSC 106, it should be understood that a scheduler may alsobe connected directly to a BTS 104. It should also be understood thatwhile scheduler 126 is depicted as a separate entity from BTS 104 andBSC 106, a scheduler may be integrated as hardware, software, and orfirmware in a BSC or in a BTS. Furthermore, it is possible that ascheduler may be implemented in another configuration altogether (suchas a system-wide scheduler, for instance).

In this context, each mobile station 102 is typically assigned a certainslot within the paging slot cycle. For instance, when a mobile station102 connects to a given base station under IS-2000, the mobile stationis typically assigned to a certain slot in the slot cycle based on themobile station's International Mobile Station Identifier (IMSI).Further, the RAN may implement a “hashing function” that effectivelyrandomizes the selection of slots such that, on average, no one slot inthe slot cycle is assigned to substantially more mobile stations thanany other slot. Other techniques for assigning slots to mobile stationsmay be used as well.

Accordingly, to help conserve battery power, a mobile station 102 in theidle state will typically monitor only its assigned slot on a givenpaging channel. Therefore, during each of its assigned slots, mobilestation 102 will scan the paging channel for any possible messages(i.e., pages). For example, when the slot cycle is 5.12 seconds, mobilestation 102 will scan the paging channel every 5.12 seconds for anypages directed to the mobile station. In practice, the duration of thescan is typically 80-120 ms, although longer or shorter scans arepossible depending on the structure of the paging channel, whether amessage has been sent, the length of the message, and the RF conditionson the mobile station's forward link, among other factors.

C. Resending Pages and Zone-Based Paging

In a further aspect of paging, a RAN will typically resend a page (andwill potentially do so a number of times) when a page fails to reach (orseemingly fails to reach) a mobile station 102. More specifically, whena mobile station 102 receives a page, it typically responds to the RANwith a page response message. Therefore, if the RAN does not receive thepage response, the RAN deduces that a failure of some sort occurred inpaging the mobile station. The failure could result from the mobilestation being temporarily out of coverage or for some other reason. Whenthis occurs, the switch in the serving system (e.g., MSC 108) preferablyattempts to re-page the mobile station. In particular, an MSC 108 maywait a predetermined period of time (ten seconds, for instance) toreceive an indication from the BTS 104 that transmitted the page record,which indicates that a page response message has been received from themobile station 102. If the MSC 108 does not receive such an indication,the MSC will resend the page to BTS 104 to again be transmitted in thecoverage area of the BTS. The MSC will repeat this process until a pageresponse message indicates that the page was successfully received or amaximum number of attempts have been made without receiving a pageresponse message. If the maximum number of attempts has been madewithout a response, then the page may be deemed to have failed.

Furthermore, when a RAN seeks to page a mobile station 102 (e.g., for anincoming call or for some other reason), a switch, such as MSC 108, maysend a page to multiple base stations, such as BTS 104, with the hopethat when the base stations broadcast the page message in multiplesectors, the mobile station 102 will receive the page message in atleast one of the sectors, and will respond. Given the scarcity of pagingchannel resources in most modern cellular networks, paging acrossmultiple sectors is typically implemented with a more-targeted pagingprocess that is commonly referred to as “zone-based paging.”

With zone-based paging, a cellular network is divided into paging zones,each with a respective zone ID, and paging is performed on a zone-basis.To facilitate this, each base station (e.g., BTS 104) in the system maybroadcast as one of its overhead parameters the zone ID for the zone inwhich the base station is located. A mobile station 102 operating in thenetwork may then programmatically monitor the zone IDs indicated in theoverhead messages and may automatically register with the network whenthey detect that they have moved into a new zone, or for other reasons.To register with the network, a mobile station may send a registrationmessage via the access channel in its current sector, and a switch inthe network would note the mobile station's registration and convey anindication of the registration to a home location register for laterreference.

With this process, the registration records thereby maintained byswitches and/or home location registers will indicate the paging zone inwhich each mobile station last registered. When a switch (e.g., MSC 108)seeks to page a mobile station, the switch may then efficiently send thepage message to just those base stations that are within the zone of themobile station's last registration, as it is likely that the mobilestation is in that zone. Further, the switch may send the page messageto the base stations in zones adjacent to the mobile station's zone oflast registration, to cover the possibility that the mobile station hasmoved to a new zone but has not yet registered its presence in the newzone.

Using the general paging strategy that is implemented in many RANsproviding IS-2000 and/or EVDO service, the network makes up to threeattempts to page a mobile station. In particular, the MSC 108 mayinitiate a first attempt by sending a page record to one or more basestations for transmission in the paging zone in which the mobile stationis registered (i.e., the base stations in the paging zone in which themobile station is registered transmit the page record). Then, if thefirst attempt is unsuccessful (i.e., the mobile station does notacknowledge the page record), the MSC initiates a second attempt byagain sending the page record to the one or more base stations fortransmission in the paging zone in which the mobile station isregistered, and possibly one or more additional base stations fortransmission in one or more adjacent zones as well. If the secondattempt also fails, then the MSC initiates a third attempt to page themobile station, which typically involves sending the page record tomultiple base stations for a system-wide transmission of the page record(i.e., in all paging zones), although it is possible that a thirdattempt may be of a different scope as well.

When a paging scheme that involves re-sending pages is employed, theswitch (e.g., MSC 52) from which a page is disseminated may track the“paging-attempt status” of a given page. The paging-attempt status for agiven page may include an “attempt count” (i.e., how many attempts havebeen made by the MSC to send a given page). For example, an MSC 52 mayinclude or have access to database that tracks the paging-attempt statusof pages initiated by the MSC. As such, when a page is successfullyreceived at the intended mobile station, and a page response message isreceived by the base station from which the page was sent, this may berelayed to the switch. The switch then knows not to initiate additionalattempts to send the page and refrains from making additional attemptsto send the page. On the other hand, if the switch does not receive anindication that the page was successful from any base station, theswitch will check the paging-attempt status, and if appropriate, sendthe page to base stations according to the zone-based paging scheme.

In a further aspect, a switch may be configured to provide the pagingattempt status of a given page to the base stations that it sends a pageto. For example, an MSC may include in or associate an indication of theattempt count with a page, when it sends a page to a base station. AnMSC may provide the paging attempt status of a page to a base stationusing other techniques as well.

Generally, it should be understood that paging schemes other thanzone-based paging may be employed, without departing from the scope ofthe invention. For instance, a base station may be paged only in thesector in which it is registered, or only in the zone in which it isregistered. As such, it is also possible that a base station may thetrack the paging-attempt status, since such embodiments may not involvecoordination between multiple base stations that send a given page, asmay be the case in a zone-based paging scheme. Further, it is possiblethat an exemplary embodiment may be implemented in a system in which nore-paging is performed. In such an embodiment, each page may simply betreated as the last attempt to send a given page.

D. Intersystem Paging

In a further aspect, a RAN may also be configured for “intersystempaging” (which may also be referred to as “border cell paging” or“BCP”). Intersystem paging techniques are typically applied when amobile station is located at or near a border between systems (each“system” including a switch and its corresponding base stations) in aRAN's coverage area. FIG. 2 is a block diagram illustrating a portion ofthe coverage area in an exemplary RAN, which includes two systems 202and 204 that serve coverage areas 203 and 205, respectively. In anexemplary embodiment, each system 202 and 204 is controlled by arespective MSC 206 and 208. Each system 202 and 204 provides service ina number of sectors that are served by the respective MSC (via one ormore base stations (not shown)). In particular, MSC 206 serves sectorsa-i, which collectively may be referred to as coverage area 203, and MSC208 serves sectors P-Z, which collectively may be referred to ascoverage area 205. In coverage area 203, sectors a-c, which are locatedat the border of the paging zones, are considered to be border sectors,and collectively are considered a border zone within system 202.Similarly, in coverage area 205, sectors P-S are considered to be bordersectors, and collectively are considered a border zone within system204.

When a mobile station is located in a border zone, the serving MSC maybe configured to send a page locally (i.e., in the sector or zone inwhich a mobile is registered), and to additionally send the page to theMSC serving the bordering system. Therefore, the mobile station can alsobe paged in the bordering system, which may improve service in the eventthat the mobile station has traveled into the coverage area of thebordering system since it last registered. Accordingly, if the mobilestation responds to a page from the serving system, then call setupproceeds normally. If, on the other hand, the mobile station responds toa page from the bordering system, the call may be transferred to thebordering system.

As an example, when a call arrives for a mobile station 210 registeredin system 202, the serving MSC 206 may determine if the mobile stationwas last registered in a border zone (i.e., if the sector in which themobile station last registered is a border sector). If the mobilestation 210 is not registered in a border zone, then the MSC 206proceeds to page the mobile station as it otherwise would (i.e., sends apage in the sector in which the mobile station is registered, andpossibly neighboring sectors as well). In the illustrated scenario,however, the mobile station 210 is registered in sector a, which is inthe border zone of system 202. Therefore, in addition to sending thepage in sector a (and possibly nearby sectors as well), the MSC 206sends an “intersystem” page to the MSC 208 serving the bordering system204. MSC 208 may then send the intersystem page to mobile station 210 inits border zone, which includes sectors P-S (via the base station orbase stations serving these sectors). If the mobile station 210 respondsto a page from system 202, then the call proceeds normally. If, on theother hand, the mobile station 210 responds to a page from system 204,the call may be transferred to system 204.

In an exemplary embodiment, intersystem paging may be implemented usingISPAGE2 functionality, as defined by the ANSI-41 protocol (which is alsoreferred to as IS-41). As such, intersystem pages may be relayed betweensystems (i.e., between MSCs) using ISPAGE2 messaging, as specified inANSI-41. ISPAGE2 and ANSI-41 are well known in the art, and thus notdescribed in detail herein. Further, it should be understood that theterm “intersystem page”, as used herein, may include any page that sentby an MSC other than the serving MSC. As such, an MSC may identify anypage it receives from another MSC, or any page it sends to another MSC,as an intersystem page.

E. Types of Pages

In an exemplary embodiment, pages may be classified as being of acertain “page-type”. As used herein, the “page-type” of a page may bedefined in a number of different ways. In some embodiments, thepage-type may be a function of the type of service (i.e., the type ofcommunication) for which a mobile station is being paged. For example, apage may be for a voice service (i.e., for a voice call other than avoice-over-IP (VOIP) call), a data service (i.e., e-mail, web browsing,Internet-based applications, VOIP, etc.), or possibly for some othertype of service. More specifically, in IS-2000 systems, where ServiceOptions (SOs) identify different types of pages, the Service Option of apage may be used to classify a page as either a voice-service page or adata-service page.

As such, a base station may be configured to identify the page-type of apage as, for example, a “voice-service” page or a “data-service” page.In other embodiments, the page-type may be a function of whether or notthe page is an “intersystem” page (i.e.; whether the page is being sentby an MSC to which the serving MSC has forwarded the page). And in otherembodiments, the page-type may be a function of both the type of service(i.e., the type of communication) for which the mobile station is beingpaged and whether or not the page is an intersystem page. Other examplesare also possible.

Importantly, in exemplary embodiments, a page for an incoming textmessage, such as a short message service (SMS) or a multimedia messagingservice (MMS) message (which, for simplicity, may both be referred toherein as “SMS-service pages” or “SMS pages”), may be classified as adata-service page, treated as a voice-service page, or treated as adistinct type of page unto themselves, according to engineering designchoice. More specifically, SMS pages technically notify the recipientmobile station of a data communication, and thus may be treated asdata-service pages. However, because an SMS center (SMSC) in a RANstores the message, and will repeatedly re-initiate a page via a networkswitch, in the event that previous attempts to send an SMS page to amobile station have failed, the PSR for SMS messages may be higher thanfor other types of data communications, and therefore SMS pages may alsobe treated as voice-service pages, which also tend tends to have ahigher PSR than data-service pages. Further, as the PSR for SMS pagesmay be higher than even the PSR for voice-service pages, SMS pages maybe treated as a separate type of page altogether.

IV. Exemplary Embodiments

In an effort to increase the probability that a page to a given mobilestation will ultimately reach the mobile station, an exemplary systemmay be configured to detect when unused space is available in a GPM, andto include multiple instances of a page record in the GPM. An exemplarysystem may take the form of a tangible computer readable medium havingprogram instructions stored thereon, which may be executed to providethe functionality described herein. An exemplary system may also takethe form of an entity or entities in a RAN, such as a switch (e.g., anMSC) or a base station (i.e., one or more BTS and/or a BSC), whichincludes or has access to such program instructions and thus providesthe functionality described herein.

FIG. 3 is flow chart illustrating a method 300 according to an exemplaryembodiment. The method 300 is preferably carried out at a base stationin a RAN, and may be implemented to take advantage of unused space in aGPM in order to help increase the paging success rate for one or moremobile stations. As shown by block 302, the method involves a basestation, before sending a general page message (GPM), making adetermination that less than the maximum number of page records arescheduled to be included in the GPM. When it is determined that lessthan the maximum number of page records are scheduled, the base stationselects at least one page record from the page records that have alreadybeen scheduled to be included in the GPM, of which to include two ormore instances, as shown by block 304. The base station then transmitsthe GPM, which accordingly includes two or more instances of the atleast one selected page record in the transmission, as shown by block306.

Generally, when a base station fills all available space in a GPM withduplicate page records before the base station sends the GPM, there is achance that during the period of time between when the base stationselects the page records to include in duplicate and when the basestation eventually sends the GPM, the base station may receive anadditional page from a switch. In this scenario, there will not be spacein the GPM for the additional page, and thus the base station will notbe able to include the additional page in the GPM, or will have toremove a duplicate page record to create space for the additional page.Accordingly, in a further aspect, an exemplary method may involvewaiting until a predetermined time before the scheduled transmission ofa GPM, which is preferably just before the scheduled transmission,before making the determination that less than a maximum number of pagerecords are included in the GPM. By waiting until just before a GPM issent, the chances of the base station receiving an additional page froma switch after filling the GPM with duplicate page records may bereduced. For instance, in an exemplary method, a base station may waituntil the slot that immediately precedes the GPM's scheduled slot beforescheduling any page records in duplicate. It should be understood,however, that the timing with which a base station determines that thereis available space in a GPM and/or schedules page records to be includedin duplicate may vary as a matter of engineering design choice.

In a further aspect, when there is space available more than one pagerecord to be scheduled in duplicate in a given GPM, the number of pagerecords that are included in duplicate may depend upon the space that isavailable in the given GPM. For example, the base station may determinehow many page records can be included in duplicate by subtracting thetotal number of page records that are scheduled for the GPM from themaximum number of page records, and select the page records to beincluded in duplicate accordingly. In an exemplary embodiment, if thetotal number of page records that are scheduled is less than or equal tothe number of page records that can be included in duplicate, then thebase station preferably includes all the scheduled page records induplicate. And, if the total number of scheduled page records is greaterthan or equal to the number of page records that can be included induplicate, then the base station selects a number of the scheduled pagerecords equal to the number of page records that can be included induplicate.

FIG. 4 is a flow chart illustrating an exemplary method 400, in whichthe number of page records included in duplicate (if any) is based atleast in part upon a determination of unused space in a GPM. Morespecifically, as shown by block 402, method 400 involves a base stationdetermining the number of page records that are scheduled to be includedin the GPM. The base station also determines the maximum number of pagerecords that can be included in the GPM, as shown in block 404. The basestation then determines an additional page-record capacity (APRC) of theGPM, which is equal to the maximum number of page records minus thenumber of page records that are scheduled, as shown by block 406.

The base station then determines whether the APRC is greater than one,as shown by block 408. If the APRC is greater than one, this means thatunused space is available for at least page record to be included induplicate. Accordingly, if the APRC is greater than or equal to one, thebase station proceeds to select one or more of the already-scheduledpage records to be included in duplicate, as shown by block 410, and toinclude two or more instances of each selected page record in thetransmission of the GPM, as shown by block 412. On the other hand, ifthe APRC is less than one, then the base station refrains from includingmultiple instances of any page record in the GPM, as shown by block 414.

FIGS. 5A and 5B are block diagrams illustrating an exemplary GPM 500before and after a base station carries out an exemplary method. Inparticular, FIG. 5A shows GPM 500 just before a base station carries outan exemplary method, such as that illustrated by FIG. 4. As shown, sixpage records (PRs) 502-512 are scheduled for transmission in GPM 500,which is formatted to include up to eight page records. Accordingly, thebase station may determine that there is space for up to two additionalpage records in GPM 500. Since the total number of scheduled pagerecords (six) is greater than the number of page records that can beincluded in duplicate (two), the base station may select one or two ofthe scheduled page records to be included in duplicate. For instance,applying method 400 of FIG. 4, the base station may select page records504 and 510, and include two instances of these page records in GPM 500,as shown by FIG. 5B.

As another specific example, FIGS. 6A and 6B are block diagramsillustrating another exemplary GPM 600 before and after a base stationcarries out an exemplary method. In particular, FIG. 6A shows GPM 600just before a base station carries out an exemplary method. As shown,GPM 600 is formatted to include up to eight page records. However, onlythree page records (PRs) 602-606 are scheduled for transmission in GPM600. Accordingly, the base station may determine that there is space forup to five additional page records in GPM 600. And since the totalnumber of page records that are scheduled (three) is less than thenumber of page records that can be included in duplicate (five), thebase station schedules all three page records 602-606 in duplicate, asshown in FIG. 6B.

In a further aspect, when the total number of page records that arescheduled in a GPM is less than the number of page records that can beincluded in duplicate, as is the case in FIG. 6A, more than twoinstances of some (or even all) of the page records may be included. Forexample, as shown in FIG. 6B, when all three page records 602-606 areincluded in duplicate, there is still space available for two more pagerecords in the GPM. Accordingly, the base station may include additionalinstances of scheduled page records in order to fill the available spacein the GPM, in an effort to further increase the PSR for the scheduledpages. For example, the base station may include three instances of pagerecords 602 and 606, and two instances of page record 604, as shown inFIG. 6C. Other examples are also possible.

When not all scheduled page records can be included in duplicate, as isthe case in FIG. 5B, the particular page records to be included induplicate may be selected using processes described herein, or possiblyusing another process altogether. Accordingly, an exemplary method mayfurther involve a selection process to determine which scheduled pagerecords should have multiple instances included. In general, theselection process may be a matter of engineering design choice, andbased on various criteria. For example, in a basic embodiment, a randomselection process may be used to randomly select page records to beincluded in duplicate (or in triplicate, and so on). Preferably,however, the selection process is a process in which the page recordsare prioritized based on various factors, such that the highest-prioritysectors can be included in duplicate. For example, if space is availablefor three page records, the page records having the three highestpriorities may be selected.

Some of the factors that may be used to prioritize page records forinclusion in duplicate will now be described. These factors may each beused alone or in combination with one or more other factors. Further,other factors may be used in addition, or in the alternative, to thosedescribed below. And in general, it should be understood that anyselection process may be incorporated, without departing from the scopeof the invention.

A. Page-Record Selection Based on Attempt Count

In some embodiments, the selection of page records for which to includemultiple instances may be based, at least in part, on the respectiveattempt counts of the already-scheduled page records. For example, whenthe transmission of a GPM will constitute the last attempt at sending apage record included therein, such a page record may be prioritized, andtwo or more instances of the page record may be included in the GPM,with the hope being that doing so will increase the chances that theintended mobile station successfully receives the page record.

More generally, page records having a higher attempt count may be givenpriority over page records having a lower attempt count. For instance,in a RAN configured to make up to three attempts to send a given page, apage record that represents the third and final attempt to page a mobilestation may be given priority over a page record that represents thesecond attempt or the first attempt to page a mobile station. Likewise,a page record that represents the second attempt to page a mobilestation may be given priority over a page record that represents thefirst attempt to page a mobile station. For example, referring back toFIG. 5A, and in particular to the six scheduled page records 502-512 ofGPM 500, consider a scenario where page records 502, 504, and 510 eachrepresent the third attempt to page the respective intended mobilestation, page record 506 represents the second attempt to page theintended mobile station, and page records 508 and 512 each represent thefirst attempt to page the respective intended mobile station.Accordingly, page records 502, 504, and 510 may be given priority overpage records 506, 508, and 512, and page record 506 may be givenpriority over page records 508 and 512.

To facilitate the determination of the attempt count for a given mobilestation, an exemplary base station may include or have access to adatabase storing attempt-count data on a per-mobile station basis. Forexample, whenever a page intended for mobile station is forwarded to abase station from an MSC, the base station may transmit the page andcheck the database to determine if an entry exists for the mobilestation. If no entry exists for the mobile station, then the basestation creates an entry for mobile station and increments the attemptcount for the mobile station (e.g., from zero attempts to one attempt).If an entry does exist for mobile station, then the base station updatesthe entry by incrementing the attempt count (e.g., from one attempt totwo attempts, or from two attempts to three attempts). Accordingly, todetermine whether or not multiple attempts have been made to page agiven mobile station, a given base station may simply access theattempt-count data for the mobile station and determine how manyattempts have been made.

Further, a RAN may be configured to reset the attempt count for a givenmobile station (or alternatively, simply delete the database entry forthe mobile station) in a number of circumstances. Generally, a RAN willreset the attempt count (or delete the attempt count data) for a givenmobile station when a page is successfully received by the mobilestation or fails to reach the mobile station (i.e., when the maximumnumber of attempts are made without success). This allows for theattempt count to start anew for subsequent pages to the same mobilestation. As such, a base station preferably resets the attempt count fora mobile station whenever the base station receives a page responsemessage from mobile station indicating that the mobile stationsuccessfully received the page.

Further, in some paging schemes (such as the typical zone-based pagingscheme described herein), multiple base stations may transmit a pageconcurrently, making it possible that the one base station maysuccessfully page a mobile station, while another is unsuccessful. Assuch, an MSC may notify a base station that unsuccessfully attempts tosend a page when another base station is successful in doing so.Accordingly, a base station may also reset its attempt count for a givenmobile station when it receives a message from an MSC (or another RANentity) indicating that the base station should reset the attempt countfor a given mobile station. In some embodiments, a message from the MSCthat indicates that a base station should reset the attempt count for agiven mobile station, may simply indicate that a page to mobile stationwas successful (which in turn indicates that the attempt count should bereset in order to avoid the attempt count carrying over to future pagesto the mobile station), or that the page failed (i.e., the maximumnumber of attempts have been made without receiving a page responsemessage at any base station).

Additionally or alternatively, a base station may implement an attempttimer, which the base station starts when a first attempt to page amobile station is made. The base station may then reset the attemptcount for the mobile station when the attempt timer expires.

In using the relative attempt counts of the page records as a basis forprioritizing the page records, the attempt count may be measured on aper-zone basis (i.e., the number of attempts made in the zone in whichthe base station carrying out the selection process is located) or on aper-page-record basis (i.e., the total number of attempts in any zone,or in other words, the paging-attempt status as described herein). Thisdistinction may be important, as it is possible that the paging-attemptstatus maintained at the MSC may differ from the attempt countmaintained by a given base station. For example, the first pagingattempt in a given zone may actually be the second or third pagingattempt overall, and thus the paging-attempt status stored at the MSCmay indicate that, on a per-page-record basis, it is the second or thirdattempt, whereas the attempt count stored at the base station mayindicate that, on a per-zone basis, that it is the first attempt to sendthe page in the given zone.

B. Page-Record Selection Based on Page-Type

In practice, the PSR may also vary between different types of pages. Forexample, it has been observed that the success rate of voice pages(i.e., pages indicating an incoming voice communication for a mobilestation) is typically higher than the success rate for data pages (i.e.,pages indicating an incoming data communication for a mobile station).This is due, at least in part, to the fact that data-service pages maybe shed in favor of voice-service pages at times when the paging channelis highly congested.

Furthermore, the PSR for intersystem pages is typically lower than thePSR for pages sent by a switching system serving the coverage area inwhich a mobile station is registered. Specifically, because intersystempages are typically sent to mobile stations located in border zonesbetween switching systems, the mobile stations may “ping-pong” betweensystems (i.e., repeatedly switch back and forth between the systems). Inthis scenario, there is a greater probability that a mobile station willdisconnect from a system before it receives a page, which in turn maydecrease the PSR for intersystem pages.

Accordingly, the selection of those page records for which to includemultiple instances may be additionally or alternatively based on thepage-type of a given page record. For example, since the PSR forvoice-service pages is typically higher than the PSR for data-servicepages, data-service page records may be given priority overvoice-service pages when selecting page records to be included induplicate. Furthermore, since the PSR is typically lower for intersystempages, intersystem pages may be given priority over non-intersystempages when selecting page records to be included in duplicate.

To facilitate selection based on page-type, a RAN may use varioustechniques to determine the page-type for a given page record. Forexample, an exemplary GPM may have a number of parameters, including aSERVICE_OPTION (SO) parameter that indicates the type of service forwhich the mobile station is being paged, and which an MSC may provide toa base station when it indicates that a mobile station needs to bepaged. Therefore, a base station may determine the page-type from theSERVICE_OPTION parameter. In an exemplary embodiment, this may involveclassifying the page as either a voice-service page or a data-servicepage based on the SERVICE_OPTION parameter. For example, the followingtable shows various Service Options codes that are defined under IS-95and IS-2000.

Service Option Service SO1 Basic Variable Rate Voice Service (8 kbps)SO2 Mobile Station Loopback (8 kbps) SO3 Enhanced Variable Rate Codec(EVRC) Voice Service (8 kbps) SO6 Short Message Services (Rate Set 1)SO9 Mobile Station Loopback (13 kbps) SO14 Short Message Services (RateSet 2) SO17 High Rate Voice Service (13 kbps) SO32 Test Data ServiceOption (TDSO) SO33 cdma2000 High Speed Packet Data Service, Internet orISO Protocol Stack SO55 Loopback Service Option (LSO) SO68 EVRC-B VoiceService (8 kbps) SO70 EVRC-WB Voice Service (8 kbps) SO32768 ProprietaryService Option (Qualcomm Inc.)According to an exemplary embodiment, the following Service Optionscodes may be classified as voice-service pages: SO1 (Basic Variable RateVoice Service (8 kbps)), SO3 (Enhanced Variable Rate Codec (EVRC) VoiceService (8 kbps)), SO17 (High Rate Voice Service (13 kbps)), SO68(EVRC-B Voice Service (8 kbps)), SO70 (EVRC-WB Voice Service (8 kbps)),and SO32768 (Proprietary Service Option for Qualcomm Inc.). Further,Service Options codes indicating data-service pages may include: SO2(Mobile Station Loopback (8 kbps)), SO9 (Mobile Station Loopback (13kbps)), SO55 (Loopback Service Option (LSO)), SO32 (Test Data ServiceOption (TDSO)), and SO33 (CDMA2000 High Speed Packet Data Service,Internet or ISO Protocol Stack).

Further, SO6 (Short Message Services (Rate Set 1)) and SO14 (ShortMessage Services (Rate Set 2)) may be classified as SMS pages. As noted,SMS pages may be treated as voice-service pages, data-service pages, oras their own distinct page-type. Accordingly, in an exemplaryembodiment, SO6 and SO14 may be treated in this manner.

Yet further, while a page record in an exemplary embodiment may take theform of a page record in a GPM, and identify the type of communicationusing the SERVICE_OPTION parameter, it should be understood that a pagemay take any form, and identify the type of communication in any manner,without departing from the scope of the invention.

Additionally or alternatively, a RAN may determine whether a page recordis an intersystem page using various techniques. For example, an MSC maydeem any page forwarded to it by another MSC to be an intersystem page.Further, to notify a base station whether or not a page is anintersystem page, an exemplary MSC may be configured to include anintersystem indicator as part of, or in conjunction with thetransmission of a page record. For instance, the MSC may include anintersystem bit in the page record, which is set to “1” if the pagerecord was forwarded to the MSC from another MSC (e.g., if the MSC didnot itself create the page record), and set to “0” if the MSC itselfcreated the page record. As such, when a BTS receives a page record, itmay check the intersystem indicator as a basis for determining thepage-type. However, it should be understood that an access network mayidentify a page as an intersystem page using any technique, withoutdeparting from the scope of the invention.

In a further aspect, page-type may be based on more than one factor. Forexample, page-type may be a function of the type of service (e.g., dataor voice) and whether or not a page is an intersystem page. Accordingly,the RAN may prioritize a page record for inclusion in duplicate based onwhether the page record is an intersystem voice-service page, anintersystem data-service page, a non-intersystem voice-service page, ora non-intersystem data-service page. Other variations, which may definepage-type based on other and/or additional factors, are also possible.

C. Page-Record Selection Based on QoS Tiers

A cellular-network service provider may offer multiple service tiers toits subscribers which provide varying quality-of-service (QoS) levels.Each service tier may specify, for example, particular services,applications, etc. that are available to a subscriber, the maximumbandwidth that is available to the subscriber for the various services,applications, etc., and/or the subscriber's priority for certain networkresources. In an exemplary embodiment, service tiers may be used toprovide QoS-differentiated service, and as such, the service tiers maytake the form of QoS tiers. Mobile stations may therefore be required togain authorization for a given QoS tier before receiving service oraccessing services and resources that are designated for the QoS tier.

When a service provider has implemented QoS tiers, the selection ofthose page records for which multiple instances should be included mayadditionally or alternatively be based on the QoS tier of the mobilestation for which the page record is intended. In particular, a pagerecord intended for a mobile station having a higher relative QoS tier(i.e., a mobile station registered to a subscriber account where thesubscriber has paid for the higher QoS tier), may be given priority ascompared to a mobile station having a lower relative QoS tier.

As a specific example, a service provider may provide three QoS tiers,which, for simplicity, may be referred to as the Gold, Silver, andBronze tiers. The Gold tier may provide the highest QoS, while theBronze tier provides the lowest QoS and the Silver tier providesintermediary QoS. Accordingly, Gold-tier users may be authorized formore services, better access to services, access to more bandwidth,guaranteed bandwidth, etc., as compared to Silver-tier users andBronze-tier users. As such, when a page record intended for a mobilestation of a Gold-tier subscriber may be given priority for inclusion induplicate over page records intended for Silver-tier and Bronze-tiersubscribers. Similarly, a page record intended for a mobile station of aSilver-tier subscriber may be given priority for inclusion in duplicateover a page record intended for a Bronze-tier subscriber. Other examplesare also possible, as QoS tiers may be defined by service providersbased on any number of factors.

D. Page-Record Selection Based on Mobile-Station RF Conditions

When a mobile station is already experiencing poor radio frequency (RF)conditions, and thus may have a weak connection to a RAN, the chances ofthe mobile station receiving a page may be reduced. Accordingly, theselection of page records for which to include multiple instances may beadditionally or alternatively based on an indication or indications ofthe RF conditions being experienced by the mobile station that is beingpaged. In particular, page records intended for mobile stationsexperiencing less-favorable RF conditions may be given priority overpage records intended for mobile stations experiencing more-favorable RFconditions.

The indication or indications of the RF conditions experienced by amobile station may take various forms. For instance, RF quality oftendegrades when a mobile station is located near the edge of a sector.Accordingly, a base station may determine that a mobile station islocated near the edge of a sector, and consider this determination toindicate that RF conditions for the mobile station are less favorable.On the other hand, a base station may interpret a determination that amobile station is not located in a border area (i.e., not near the edgeof a sector) to indicate that the mobile station is experiencingmore-favorable RF conditions.

In one embodiment, a base station may determine that a mobile station isnear the edge of a sector by determining the elapsed time since alast-received zone-based registration message from the mobile station.Since zone-based registration messages are sent whenever a mobilestation enters a new sector (and thus are assumed to have been sent whenthe mobile station was at or near the edge of the sector), the basestation may interpret a determination that the elapsed time is less thana certain threshold as an indication that the mobile station is near theedge of a sector, and thus likely to be experiencing less favorable RFconditions. The base station may then give priority to such mobilestations, in an effort to increase the probability that the mobilestation receives the page.

In other embodiments, a base station may additionally or alternativelyutilize other indications of the RF conditions for a mobile station toprioritize for inclusion in duplicate. For example, the base station mayuse parameters included in a radio-environment report (RE-Report) from amobile station that are indicative of RF quality. In particular, the RANmay give priority to page records intended for mobile stations havinglower relative signal strength, as indicated by theACTIVE_PILOT_STRENGTH parameter in the last-received RE-Report from therespective mobile stations.

Further, the above indications of the RF conditions being experienced bya mobile station may be used in combination with other indications ofthe RF conditions a mobile station is experiencing. And in general, abase station may use any indication or indications of the quality of theRF signal being experienced by the mobile station, without departingfrom the scope of the invention. Further description of how a RAN maydetermine the RF conditions being experienced by a mobile station may bedetermined is provided in the co-owned U.S. patent application Ser. No.12/690,629, which is incorporated by reference herein in its entirety.

E. Page-Record Selection Based on Hybrid Capabilities of a MobileStation

In some wireless communication systems or markets, a wireless serviceprovider may implement more than one type of air interface protocolwithin a single system. For example, a carrier may support one oranother version of CDMA, such as IS-2000, for both circuit-cellularvoice and data traffic, as well as a more exclusivelypacket-data-oriented protocol such as IS-856. In such a “hybrid system,”a mobile station might not only hand off between coverage areas under acommon air interface protocol (e.g., between IS-2000 sectors) but mayalso hand off between the different air interface protocols, such asbetween IS-2000 and IS-856. A mobile station capable of communicating onmultiple air interface protocols of a hybrid system is referred to as a“hybrid mobile station.”

In typical operation, a hybrid mobile station remains in an IS-2000 idlestate (i.e., is registered with the IS-2000 system), while it is engagedin an IS-856 call. As such, the mobile station continues to monitor thepaging and control channels in the IS-2000 system, in search of anyincoming pages, voice calls, SMS messages, or the like, and to monitorIS-2000 pilot signals. More specifically, during an active IS-856communication (i.e., data session), a mobile station has its antenna andreceiver tuned to the RF frequency of the IS-856 interface. However, inorder to scan the IS-2000 interface according to its assigned pagingslot (e.g., every 5.12 seconds), the mobile station must periodicallytune to the RF frequency of the IS-2000 interface and tune away from theIS-856 interface for the duration of the scan interval. These slot-cyclescans, commonly referred to as “tuneaway scans,” can have an impact onquality and throughput of IS-856 communications.

In the event that a hybrid mobile station does not receive a GPM duringits assigned paging slot cycle, it will wait for additional paging slotcycles until it receives a GPM. In current hybrid systems, a drop-calltimer may expire while the mobile station waits, which causes the IS-856communication to be dropped. Under IS-856, when the serving base stationdoes not receive any DRC messages from the mobile station for threeconsecutive time slots (i.e., 240 ms), the base station starts adrop-call timer, which is typically eight to ten seconds in duration.When the drop-call timer expires, the base station ends thecommunication (i.e., the call is dropped). For example, when the mobilestation tunes away to listen for an IS-2000 page message, the mobilestation is no longer communicating on the IS-856 interface, and thuswill cease sending DRC messages to the access network on the IS-856interface. When the serving IS-856 base station does not receive any DRCmessage for three consecutive frames (i.e., 240 ms), the base stationstarts a drop-call timer, which in practice, is typically eight to tenseconds in duration.

If a hybrid mobile station receives a page record as expected, then themobile station may tune back to the IS-856 and continue its call.However, if the mobile station does not receive a page message, andremains tuned away until a page message is received, the drop-call timermay expire, causing the call to be dropped. For example, if thedrop-call timer is eight seconds, and the mobile station has to wait10.24 seconds for two page slot cycles (5.12 seconds each) or longerbefore it successfully receives a page message, the drop-call timer willexpire and the IS-856 call may be dropped. Other examples are alsopossible, and it should be understood that an exemplary embodiment maybe implemented in conjunction with a drop-call timer of any duration.

In view of the foregoing, it may be desirable to prioritize page recordsintended for hybrid mobile station, in an effort to increase theprobability that a hybrid mobile station receives a page, and avoids theabove scenario where a call may be dropped. Accordingly, the selectionof page records for which to multiple instances should be included maybe additionally or alternatively be based on whether or not the mobilestation for which the page is intended is a hybrid mobile station.

To determine whether or not a given mobile station is a hybrid mobilestation, the access network may perform a look-up, based on the mobilestation's identifier, such as the Electronic Serial Number (ESN) of themobile station, which is typically a 32-bit number that is assigned bythe manufacturer of the mobile station and uniquely identifies themobile station. Accordingly, each switch in the access network (e.g.,each MSC) may include a database that maps the access-terminalidentifier (e.g., the ESN) to the model number and capabilities of themodel, including whether or not it is capable of hybrid IS-2000/IS-856operation. In practice, this database is typically populated and/orupdated by the service provider, although it may be maintained and/orcreated in any manner, and may be stored in an entity other than aswitch, without departing from the scope of the invention. It should beunderstood, however, that any technique may be used to determine whetheror not a mobile station is a hybrid, without departing from the scope ofthe invention.

F. Selection from Between Page Records Having Equal Priority

It is possible that even after a base station considers some or all ofthe factors described above, the number of page records having apriority that qualifies them to have multiple instances included maystill be greater than the number of spaces available for duplicateinstances of page records having the given priority. In this scenario,the base station may resort to a random selection process to select fromthe page records having the same priority.

For instance, referring back to FIG. 4A, since six page records 402-412are included in GPM 400, there is only space for up to two page recordsto be included in duplicate. However, consider a scenario where thereare three page records 402, 404, and 410 that represent the third andfinal attempt to page the respective intended mobile stations. As such,the base station must select two of these three page records 402, 404,and 410, which based on attempt count alone, are of equal priority. Thebase station may simply use a random selection process, and/or may useany of the other factors described herein, alone or in combination, toselect between page records having the same priority.

It should be understood that before resorting to random selection, anexemplary base station may go through a hierarchy of factors, in aneffort to prioritize the scheduled page records. For example, consider aGPM that is formatted to include up to eight page records, and whichinitially includes one page record that represents the third attempt topage a mobile station, three page records that represent the secondattempt to page the respective mobile stations, and one page record thatrepresents the first attempt to page a mobile station. Further, thethree page records that represent a second attempt are all intended formobile stations associated with a subscriber who has paid for aGold-tier QoS plan, and are all being sent in effort to initiate a voicecall. As there is space in the GPM for up to three page records to beincluded in duplicate, the base station may first select the page recordthat represents the third attempt, as according to an exemplaryembodiment, this page record has priority over those page records thatrepresent the second attempt or first attempt to page a mobile station.This leaves space for two of the three page records that represent asecond attempt to be included in duplicate.

Since there are three page records that all represent a second attemptto page a mobile station, the base station needs to determine which twoof these three page records should be included in duplicate.Accordingly, the base station may step through a hierarchy of one ormore additional factors in an attempt to prioritize these three pagerecords. For example, when one or more page records need to be selectedfrom among page records having the same attempt number, the base stationmay be configured to use page-type as a selection factor. Further, whenone or more page records need to be selected from among page recordshaving the same attempt number and the same page-type, the base stationmay be configured to use the QoS level associated with the mobilestation as a selection factor.

In the above example, even after stepping through the hierarchy ofattempt count, page-type, and QoS level, there are three page recordsthat have the same priority, and all qualify to be one of the tworemaining page records included in duplicate. Therefore, since nodefinite selection results even after the base station considers theadditional factors, the base station may resort to a random selectionprocess in order to select the two of these three page records to beincluded in duplicate.

It should be understood the arrangements and functions described hereinare presented for purposes of example only, and that numerous variationsare possible. For instance, elements can be added, omitted, combined,distributed, reordered, or otherwise modified. Further, where thisdocument mentions functions that can be carried out by a device or otherentity, it should be understood that the functions may be implemented bysoftware (e.g., machine language instructions stored in data storage andexecutable by a processor), firmware, and/or hardware.

We claim:
 1. A paging method in a radio access network, the methodcomprising: before a transmission of a general page message (GPM) thatis formatted to include up to a maximum number of page records, making adetermination that less than the maximum number of page records arescheduled to be included in the GPM; in response to the determinationthat less than the maximum number of page records are scheduled to beincluded in the GPM, selecting, from one or more page records that arescheduled to be included in the GPM, at least one page record for whichto include two or more instances in the GPM, wherein the selecting ofthe at least one page record for which to include two or more instancesin the GPM is based at least in part on a comparison of page-types ofthe scheduled page records; and transmitting the GPM, wherein two ormore instances of the at least one selected page record are included inthe transmission of the GPM.
 2. The method of claim 1, wherein themaximum number of page records is eight.
 3. The method of claim 1,wherein the GPM is transmitted in an 80 ms paging-channel slot.
 4. Themethod of claim 1, further comprising waiting until a predetermined timebefore transmission of the GPM is scheduled, before making thedetermination that less than a maximum number of page records areincluded in the GPM.
 5. The method of claim 1, wherein making thedetermination that less than the maximum number of page records arescheduled to be included in the GPM: determining a total number of pagerecords that are scheduled to be included in the GPM; and determiningthat the total number of page records that are scheduled to be includedin the GPM is less than the maximum number of page records.
 6. Themethod of claim 5, wherein selecting, from the page records that arescheduled to be included in the GPM, the at least one page record forwhich to include two or more instances in the GPM comprises: determininga number of page records that can be included in duplicate bysubtracting the total number of page records that are scheduled to beincluded in the GPM from the maximum number of page records; and fromthe page records that are scheduled to be included in the GPM, selectingup to the number of page records that can be included in duplicate, tobe included in duplicate in the GPM.
 7. The method of claim 6, whereinselecting up to the number of page records that can be included induplicate comprises: if the total number of page records that arescheduled to be included in the GPM is less than or equal to the numberof page records that can be included in duplicate, then selecting allthe scheduled page records that are scheduled to be included in the GPM;and if the total number of page records that are scheduled to beincluded in the GPM is greater than or equal to the number of pagerecords that can be included in duplicate, then selecting a number ofthe scheduled page records equal to the number of page records that canbe included in duplicate.
 8. The method of claim 1, wherein theselecting of the at least one page record for which to include two ormore instances in the GPM is further based at least in part on a randomselection process.
 9. The method of claim 1, wherein the selecting ofthe at least one page record for which to include two or more instancesin the GPM is further based at least in part on attempt counts for theone or more of the page records that are scheduled to be included in theGPM.
 10. The method of claim 1, wherein the selecting of the at leastone page record for which to include two or more instances in the GPM isfurther based at least in part on a comparison of service-tiersassociated with the mobile stations to which the scheduled page recordsare directed.
 11. The method of claim 1, wherein each of the scheduledpage records wherein the selecting of the at least one page record forwhich to include two or more instances in the GPM is further based atleast in part on RF conditions being experienced by the mobile stationsto which the scheduled page records are directed.
 12. The method ofclaim 1, wherein the selecting of the at least one page record for whichto include two or more instances in the GPM is further based at least inpart on whether or not each of the mobile stations to which thescheduled page records are directed is hybrid mobile station.
 13. Apaging system comprising: a tangible computer-readable medium; andprogram instructions stored on the tangible computer-readable medium andexecutable by at least one processor to: (a) before a transmission of ageneral page message (GPM) that is formatted to include up to a maximumnumber of page records, make a determination that less than the maximumnumber of page records are scheduled to be included in the GPM; (b) inresponse to the determination that less than the maximum number of pagerecords are scheduled to be included in the GPM, select at least onepage record from one or more page records that are scheduled to beincluded in the GPM, for which to include two or more instances in theGPM, wherein the selection of the at least one page record for which toinclude two or more instances in the GPM is based at least in part on acomparison of page-types of the scheduled page records; and (c) initiatethe transmission of the GPM, wherein two or more instances of the atleast one selected page record are included in the transmission of theGPM.
 14. The system of claim 13, wherein selection of the at least onepage record for which to include two or more instances in the GPM isfurther based at least in part on a random selection process.
 15. Thesystem of claim 13, wherein selection of the at least one page recordfor which to include two or more instances in the GPM is further basedat least in part on attempt counts for the one or more of the pagerecords that are scheduled to be included in the GPM.
 16. The system ofclaim 13, wherein selection of the at least one page record for which toinclude two or more instances in the GPM is further based at least inpart on a comparison of service-tiers associated with the mobilestations to which the scheduled page records are directed.
 17. Thesystem of claim 13, wherein each of the scheduled page records whereinselection of the at least one page record for which to include two ormore instances in the GPM is further based at least in part on RFconditions being experienced by the mobile stations to which thescheduled page records are directed.
 18. The system of claim 13, whereineach of the scheduled page records wherein selection of the at least onepage record for which to include two or more instances in the GPM isfurther based at least in part on whether or not each of the mobilestations to which the scheduled page records are directed is hybridmobile station.